1. Field of the Invention
The present invention generally relates to a heat exchanger, more particularly, to a condenser suitable for use in an automotive air conditioning system.
2. Description of the Prior Art
Japanese Utility Model Application Publication No. 58-104867 discloses a condenser suitable for use in an automotive air conditioning system. With reference to FIG. 1 of this first prior art device, the condenser includes serpentine-shaped flat pipe 110 for conducting a refrigerant therethrough. Serpentined flat pipe 110 comprises a plurality of straight portions 110a located parallel to each other. Straight portions 110a fixedly sandwich corrugated fins 111 therebetween. Inlet and outlet unions 112 and 113 are fixedly and hermetically connected at both open ends of serpentined flat pipe 110 respectively.
In this first prior art device, reduction of the gap H' between straight portions 110a is restricted because the flat pipe 110 must be bent into the serpentine shape, thereby limiting to elevation of heat radiating efficiency of fin 111. Further, a high flow resistance is encountered when the refrigerant flows through flat pipe 110, because the refrigerant must flow through each straight position 110a in series from the inlet to the exit union. Finally, this structure is thereby limited by the gap H', i.e., distance between flat pipes and is further limited by the heat radiating efficiency of fins 111.
To overcome the above-mentioned defects, Japanese Patent Application Publication No. 63-112065 discloses a second prior art device. With reference to FIG. 2, the condenser includes a plurality of flat pipes 120 of aluminum alloy located parallel to each other. Each flat pipe 120 conducts refrigerant therethrough. Flat pipes 120 fixedly sandwich corrugated fins 121 of clad aluminum alloy therebetween.
First header pipe 122 having an open end and a closed end is mounted perpendicular to flat pipes 120 and is fixedly and hermetically connected to one end of each flat pipe 120. Inlet union 122a is fixedly and hermetically connected to the open end of first header pipe 122. Second header pipe 123, also having an open end and a closed end, is mounted perpendicular to flat pipes 120 and is fixedly and hermetically connected to the other end of each flat pipe 120. Outlet union 123a is fixedly and hermetically connected to the open end of second header pipe 123.
In the construction of the second prior art device, the refrigerant in first header pipe 122 first flows into inlet union 122a, then distributively flows into each flat pipe 120, and sequentially flows together into second header pipe 123, so that the flow resistance generated as the refrigerant flows through flat pipe 120 is remarkably less than the flow resistance in the first prior art device. Accordingly, the diameter of the flat pipes 120 can be reduced without generating high flow resistance. Consequently, the number of flat pipes 120 can be increased without increasing the size of the condenser, that is, the gap H in the second prior art device is less than the gap H' in the first prior art device. As a result, a condenser having a greater ability to exchange heat is obtained.
In the second prior art device, inlet and outlet unions 122a, 123a are fixedly and hermetically connected to each open end of first and second header pipes 122 and 123 respectively, for example, by brazing. That is, two hermetically joined portions between the union and the header pipe exist.
However, it is desirable to provide only one union element to the header pipes, because the number of potentially defective hermetically joined portions is proportional to the number of hermetically joined portions.